Method for producing organic electroluminescent device

ABSTRACT

A method for producing an organic electroluminescent device includes the step of forming a driving circuit layer on a substrate; the step of forming an inorganic protective layer on the driving circuit layer; the step of forming an organic flattening layer on the inorganic protective layer; the step of reducing moisture contained in the organic flattening layer; the step of forming an organic electroluminescent element layer on the organic flattening layer after the step of reducing moisture; and, after the organic flattening layer is formed but before the organic flattening layer is heated, the step of forming an organic polymer film covering the organic flattening layer and the step of removing the organic polymer film.

TECHNICAL FIELD

The present invention relates to an organic electroluminescent device(e.g., an organic EL display device and an organic EL illuminationdevice) and a method for producing the same.

BACKGROUND ART

Organic EL (Electro-Luminescent) display devices start being put intopractical use. One feature of an organic EL display device is beingflexible. An organic EL display device includes, in each of pixels, atleast one organic EL element (Organic Light Emitting Diode: OLED) and atleast one TFT (Thin Film Transistor) controlling an electric current tobe supplied to each of the at least one OLED). Hereinafter, an organicEL display device will be referred to as an “OLED display device”. Suchan OLED device including a switching element such as a TFT or the likein each of OLEDs is called an “active matrix OLED display device”. Asubstrate including the TFTs and the OLEDs will be referred to as an“element substrate”.

An OLED (especially, an organic light emitting layer and a cathodeelectrode material) is easily influenced by moisture to be deterioratedand to cause display non-unevenness. One technology developed in orderto provide an encapsulation structure that protects the OLED againstmoisture while not spoiling the flexibility of the OLED display deviceis a thin film encapsulation (TFE) technology. According to the thinfilm encapsulation technology, inorganic barrier layers and organicbarrier layers are stacked alternately to allow thin films to provide asufficient level of water vapor barrier property. From the point of viewof moisture-resistant reliability of the OLED display device, such athin film encapsulation structure is typically required to have a WVTR(Water Vapor Transmission Rate) less than, or equal to, 1×10⁻⁴ g/m²/day.

A thin film encapsulation structure used in OLED display devicescommercially available currently includes an organic barrier layer(polymer barrier layer) having a thickness of about 5 μm to about 20 μm.Such a relatively thick organic barrier layer also has a role offlattening a surface of the element substrate. However, such a thickorganic barrier layer involves a problem that the bendability of theOLED display device is limited.

There is also a problem that the mass-productivity is low. Therelatively thick organic barrier layer described above is formed by useof a printing technology such as an inkjet method, a microjet method orthe like. By contrast, the inorganic barrier layer is formed by a thinfilm deposition technology in a vacuum atmosphere (e.g., less than, orequal to, 1 Pa). The formation of the organic barrier layer by use of aprinting method is performed in the air or a nitrogen atmosphere,whereas the formation of the inorganic barrier layer is performed invacuum. Therefore, the element substrate is put into, and out of, avacuum chamber during the formation of the thin film encapsulationstructure, which decreases the mass-productivity.

In such a situation, as disclosed in, for example, Patent Document 1, afilm formation device capable of producing an inorganic barrier layerand an organic barrier layer continuously has been developed.

Patent Document 2 discloses a thin film encapsulation structureincluding a first inorganic material layer, a first resin member and asecond inorganic material layer provided on the element substrate inthis order. In this thin film encapsulation structure, the first resinmember is present locally, namely, around a protruding portion of thefirst inorganic material layer (first inorganic material layer coveringa protruding component). According to Patent Document 2, the first resinmember is present locally, namely, around the protruding component,which may not be sufficiently covered with the first inorganic materiallayer. With such a structure, entrance of moisture or oxygen via thenon-covered portion is suppressed. In addition, the first resin memberacts as an underlying layer for the second inorganic material layer.Therefore, the second inorganic material layer is properly formed andproperly covers a side surface of the first inorganic material layerwith an expected thickness. The first resin member is formed as follows.An organic material heated and vaporized to be mist-like is suppliedonto an element substrate maintained at a temperature lower than, orequal to, room temperature. As a result, the organic material iscondensed and put into drops on the substrate. The organic material indrops moves on the substrate by a capillary action or a surface tensionto be present locally, namely, at a border between a side surface of theprotruding portion and a surface of the element substrate. Then, theorganic material is cured to form the first resin member at the border.Patent Document 3 also discloses an OLED display device having a similarthin film encapsulation structure. Patent Document 4 discloses a filmformation device usable to produce an OLED display device.

CITATION LIST Patent Literature

Patent Document No. 1: Japanese Laid-Open Patent Publication No.2013-186971

Patent Document No. 2: WO2014/196137 Patent Document No. 3: JapaneseLaid-Open Patent Publication No. 2016-39120

Patent Document No. 4: Japanese Laid-Open Patent Publication No.2013-64187

SUMMARY OF INVENTION Technical Problem

The thin film encapsulation structure described in each of PatentDocuments 2 and 3 does not include a thick organic barrier layer, andtherefore, are considered to improve the bendability of the OLED displaydevice. In addition, since the inorganic barrier layer and the organicbarrier layer may be formed continuously, the mass-productivity is alsoimproved.

However, according to the studies made by the present inventors, anorganic barrier layer formed by the method described in Patent Document2 or 3 has a problem of not providing a sufficient level ofmoisture-resistant reliability.

In the case where an organic barrier layer is formed by use of aprinting method such as an inkjet method or the like, it is possible toform the organic barrier layer only in an active region on the elementsubstrate (the active region may also be referred to as an “elementformation region” or a “display region”) but not in a region other thanthe active region. In this case, in the vicinity of the active region(outer to the active region), there is a region where the firstinorganic material layer and the second inorganic material layer are indirect contact with each other, and the organic barrier layer is fullyenclosed by the first inorganic material layer and the second inorganicmaterial layer and is insulated from the outside of the first inorganicmaterial layer and the second inorganic material layer.

By contrast, according to the method for forming the organic barrierlayer described in Patent Documents 2 or 3, a resin (organic resin) issupplied to the entire surface of the element substrate, and the surfacetension of the resin in a liquid state is used to distribute the resinat the border between the surface of the element substrate and the sidesurface of the protruding portion on the surface of the elementsubstrate. Therefore, the organic barrier layer may also be formed in aregion other than the active region (the region other than the activeregion may also be referred to as a “peripheral region”), namely, aterminal region where a plurality of terminals are located and a leadwire region where lead wires extending from the active region to theterminal region are formed. Specifically, the resin is present locally,namely, at, for example, the border between the surface of the elementsubstrate and side surfaces of the lead wires or side surfaces of theterminals. In this case, an end of the organic barrier layer formedalong the lead wires is not enclosed by the first inorganic barrierlayer and the second inorganic barrier layer, but is exposed to the air(ambient atmosphere).

The organic barrier layer is lower in the water vapor barrier propertythan the inorganic barrier layer. Therefore, the organic barrier layerformed along the lead wires acts as a route that leads the water vaporin the air to the active region.

Herein, the problems of the thin film encapsulation structure preferablyusable for a flexible organic EL display device have been described. Thethin film encapsulation structure is usable for another organic ELdevice such as an organic EL illumination device or the like as well asfor the organic EL display device.

The present invention, made to solve the above-described problems, hasan object of providing a method for producing an organic EL deviceincluding a thin film encapsulation structure that includes a relativelythin organic barrier layer and is improved in the mass-productivity andthe moisture-resistant reliability.

Solution to Problem

A method for producing an organic EL device according to an embodimentof the present invention is a method for producing an organic EL deviceincluding a substrate; a driving circuit layer including a plurality ofTFTs formed on the substrate, a plurality of gate bus lines and aplurality of source bus lines each connected with either one of theplurality of TFTs, a plurality of terminals, and a plurality of leadwires connecting each of the plurality of terminals with either one ofthe plurality of gate bus lines or either one of the plurality of sourcebus lines; an inorganic protective layer formed on the driving circuitlayer and exposing at least the plurality of terminals; an organicflattening layer formed on the inorganic protective layer; an organic ELelement layer formed on the organic flattening layer and including aplurality of organic EL elements each connected with either one of theplurality of TFTs; and a thin film encapsulation structure formed tocover the organic EL element layer. The method includes step A offorming the driving circuit layer on the substrate; step B of formingthe inorganic protective layer on the driving circuit layer; step C offorming the organic flattening layer on the inorganic protective layer;step D of heating the organic flattening layer to a temperature higherthan, or equal to, 200° C.; step E of forming the organic EL elementlayer on the organic flattening layer after the step of heating; andstep C1 of forming an organic polymer film covering the organicflattening layer and step C2 of removing the organic polymer film, thestep C1 and the step C2 being performed after the step C but before thestep D.

In an embodiment, the method further includes the step of storing ortransporting the substrate having the organic polymer film formedthereon between the step C1 and the step C2.

In an embodiment, the step C1 includes the step of supplying a solutionof the organic polymer film onto the organic flattening layer.

In an embodiment, the organic polymer film is formed of a water-solublepolymer.

In an embodiment, the step C2 includes the step of dissolving theorganic polymer film in an aqueous solvent.

In an embodiment, the water-soluble polymer is poly(vinyl alcohol).

In an embodiment, the organic flattening layer is formed of aphotosensitive resin.

In an embodiment, the organic flattening layer is formed of polyimide.

In an embodiment, as seen in a direction of normal to the substrate, theorganic flattening layer is formed in a region where the inorganicprotective layer is formed, the plurality of organic EL elements areformed in a region where the organic flattening layer is formed, and anouter perimeter of the thin film encapsulation structure crosses theplurality of lead wires and is present between an outer perimeter of theorganic flattening layer and an outer perimeter of the inorganicprotective layer; and in a region where the inorganic protective layerand the first inorganic barrier layer are in direct contact with eachother on the plurality of lead wires, a tapering angle of a side surfaceof a cross-section of the first inorganic barrier layer taken along aplane parallel to a width direction of the plurality of lead wires issmaller than 90 degrees.

In an embodiment, the tapering angle of the side surface of the firstinorganic barrier layer is smaller than 70 degrees.

In an embodiment, the method further includes step F of, after the stepE, forming the first inorganic barrier layer selectively in an activeregion where the plurality of organic EL elements are formed; step G of,after the step F, locating the substrate in a chamber and supplying avapor-like or mist-like photocurable resin into the chamber; step H ofcondensing the photocurable resin on the first inorganic barrier layersuch that the photocurable resin is not present on a part of the firstinorganic barrier layer, the part having the tapering angle smaller than90 degrees; and step I of, after the step H, irradiating the condensedphotocurable resin with light to form the organic barrier layer of thephotocurable resin.

In an embodiment, the method further includes step F, after the step E,forming the first inorganic barrier layer selectively in an activeregion where the plurality of organic EL elements are formed; step G of,after the step F, locating the substrate in a chamber and supplying avapor-like or mist-like photocurable resin into the chamber; step H ofcondensing the photocurable resin on the first inorganic barrier layerto form a liquid film; step I of irradiating the liquid film of thephotocurable resin with light to form a photocurable resin layer; andstep J of partially asking the photocurable resin layer to form theorganic barrier layer.

Advantageous Effects of Invention

An embodiment of the present invention provides a method for producingan organic EL device including a thin film encapsulation structure thatincludes a relatively thin organic barrier layer and is improved in themass-productivity and the moisture-resistant reliability.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1(a) is a schematic partial cross-sectional view of an activeregion of an OLED display device 100 according to an embodiment of thepresent invention; and FIG. 1(b) is a partial cross-sectional view of aTFE structure formed on an OLED 3.

FIG. 2 is a schematic plan view of the OLED display device 100 accordingto an embodiment of the present invention.

FIG. 3(a) and FIG. 3(b) are each a schematic cross-sectional view of theOLED display device 100; FIG. 3(a) is a cross-sectional view taken alongline 3A-3A′ in FIG. 2, FIG. 3(b) is a cross-sectional view taken alongline 3B-3B′ in FIG. 2, and FIG. 3(c) is a cross-sectional view showing atapering angle θ of a side surface of each of layers.

FIG. 4(a) through FIG. 4(d) are each a schematic cross-sectional view ofthe OLED display device 100; FIG. 4(a) is a cross-sectional view takenalong line 4A-4A′ in FIG. 2, FIG. 4(b) is a cross-sectional view takenalong line 4B-4B′ in FIG. 2, FIG. 4(c) is a cross-sectional view takenalong line 4C-4C′ in FIG. 2, and FIG. 4(d) is a cross-sectional viewtaken along line 4D-4D′ in FIG. 2.

FIG. 5(a) and FIG. 5(b) are respectively schematic cross-sectional viewsof OLED display devices 100B1 and 100B2 in comparative examples, thecross-sectional views corresponding to FIG. 4(b).

FIG. 6 is a schematic plan view of an OLED display device 100C in acomparative example.

FIG. 7(a) and FIG. 7(b) are each a schematic cross-sectional view of theOLED display device 100C; FIG. 7(a) is a cross-sectional view takenalong line 7A-7A′ in FIG. 6, and FIG. 7(b) is a cross-sectional viewtaken along line 7B-7B′ in FIG. 6.

FIG. 8(a) through FIG. 8(c) are each a schematic cross-sectional view ofthe OLED display device 100C; FIG. 8(a) is a cross-sectional view takenalong line 8A-8A′ in FIG. 6, FIG. 8(b) is a cross-sectional view takenalong line 8B-8B′ in FIG. 6, and FIG. 8(c) is a cross-sectional viewtaken along line 8C-8C′ in FIG. 6.

FIG. 9(a) and FIG. 9(b) are each a schematic cross-sectional view of anexample of TFT included in an OLED display device in an embodiment.

FIG. 10(a) through FIG. 10(c) are each a schematic cross-sectional viewof another OLED display device in an embodiment, the schematiccross-sectional views respectively corresponding to FIG. 4(b) throughFIG. 4(d).

FIG. 11(a) and FIG. 11(b) each schematically show a structure of a filmformation device 200; FIG. 11(a) shows a state of the film formationdevice 200 in a step of condensing a photocurable resin on a firstinorganic barrier layer, and FIG. 11(b) shows a state of the filmformation device 200 in a step of curing the photocurable resin.

DESCRIPTION OF EMBODIMENTS

Hereinafter, OLED display devices and methods for producing the sameaccording to embodiments of the present invention will be described withreference to the drawings. In the following, an OLED display deviceincluding a flexible substrate will be described. An embodiment of thepresent invention is not limited to being directed to an organic ELdisplay device, and may be directed to another organic EL device such asan organic EL illumination device. The present invention is not limitedto any of the embodiments described below.

First, a basic structure of an OLED display device 100 according to anembodiment of the present invention will be described with respect toFIG. 1(a) and FIG. 1(b). FIG. 1(a) is a schematic partialcross-sectional view of an active region of the OLED display device 100according to an embodiment of the present invention. FIG. 1(b) is apartial cross-sectional view of a TFE structure 10 formed on an OLED 3.

The OLED display device 100 includes a plurality of pixels, and each ofthe pixels includes at least one organic EL element (OLED). Herein, astructure corresponding to one OLED will be described for simplicity.

As shown in FIG. 1(a), the OLED display device 100 includes a flexiblesubstrate (hereinafter, may be referred to simply as a “substrate”) 1, acircuit 2 including a TFT that is formed on the substrate 1 (the circuitmay be referred to as a “driving circuit” or a “back plane circuit”), aninorganic protective layer 2Pa formed on the circuit 2, an organicflattening layer 2Pb formed on the inorganic protective layer 2Pa, theOLED 3 formed on the organic flattening layer 2Pb, and the TFE structure10 formed on the OLED 3. The OLED 3 is, for example, of a top emissiontype. An uppermost portion of the OLED 3 is, for example, a topelectrode or a cap layer (refractive index adjusting layer). A layerincluding a plurality of the OLEDs 3 may be referred to as an “OLEDlayer 3”. An optional polarization plate 4 is located on the TFEstructure 10. The circuit 2 and the OLED 3 may share at least onecomponent. In addition, a layer having a touch panel function may belocated between the TFE structure 10 and the polarization plate 4.Namely, the OLED display device 100 may be altered to a display deviceincluding an on-cell type touch panel.

The substrate 1 is, for example, a polyimide film having a thickness of15 The circuit 2 including the TFT has a thickness of, for example, 4The inorganic protective layer 2Pa has a structure of, for example,SiN_(x) layer (500 nm)/SiO₂ layer (100 nm) (top layer/bottom layer).Alternatively, the inorganic protective layer 2Pa may have a three-layerstructure of SiO₂ layer/SiN_(x) layer/SiO₂ layer. The thickness of thelayers are, for example, 200 nm/300 nm/100 nm. The organic flatteninglayer 2Pb is, for example, a photosensitive acrylic resin layer or aphotosensitive polyimide layer having a thickness of 4 μm. The OLED 3has a thickness of, for example, 1 μm. The TFE structure 10 has athickness of, for example, less than, or equal to, 2.5 μm.

FIG. 1(b) is a partial cross-sectional view of the TFE structure 10formed on the OLED 3. A first inorganic barrier layer (e.g., SiN_(x)layer) 12 is formed immediately on the OLED 3. An organic barrier layer(e.g., acrylic resin layer) 14 is formed on the first inorganic barrierlayer 12. A second inorganic barrier layer (e.g., SiN_(x) layer) 16 isformed on the organic barrier layer 14.

The first inorganic barrier layer 12 is, for example, an SiN_(x) layerhaving a thickness of 1.5 μm. The second inorganic barrier layer 16 is,for example, an SiN_(x) layer having a thickness of 800 nm. The organicbarrier layer 14 is, for example, an acrylic resin layer having athickness less than 100 nm. The first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 independently have a thickness of 200nm or greater and 1500 nm or less. The organic barrier layer 14 has athickness of 50 nm or greater and less than 200 nm. The TFE structure 10has a thickness of preferably 400 nm or greater and less than 3 μm, andmore preferably of 400 nm or greater and 2.5 μm or less.

The TFE structure 10 is formed to protect the active region (see activeregion R1 in FIG. 2) of the OLED display device 100. At least in theactive region R1, there are the first inorganic barrier layer 12, theorganic barrier layer 14 and the second inorganic barrier layer 16formed in this order on the OLED 3, with the first inorganic barrierlayer 12 being closest to the OLED 3. The organic barrier layer 14 isnot present as a film covering the entirety of the active region R1, buthas an opening. A part of the organic barrier layer 14 other than theopening, namely, a part actually formed of an organic film, will bereferred to as a “solid portion”. The organic barrier layer 14 may beformed by, for example, the method described in Patent Document 1 or 2or by use of a film formation device 200 described below.

The “opening” (may be referred to also as a “non-solid portion”) doesnot need to be enclosed by the solid portion, but may have a cutout orthe like. In the opening, the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 are in direct contact with each other.Hereinafter, a portion where the first inorganic barrier layer 12 andthe second inorganic barrier layer 16 are in direct contact with eachother will be referred to as an “inorganic barrier layer joint portion”.

Now, with reference to FIG. 2 and FIG. 3, a structure of the OLEDdisplay device 100 and a method for producing the same according to anembodiment of the present invention will be described.

FIG. 2 is a schematic plan view of the OLED display device 100 accordingto an embodiment of the present invention. With reference to FIG. 3(a)through FIG. 3(c) and FIG. 4(a) through FIG. 4(d), a cross-sectionalstructure of the OLED display device 100 will be described. FIG. 3(a)and FIG. 3(b) are each a schematic cross-sectional view of the OLEDdisplay device 100. FIG. 3(a) is a cross-sectional view taken along line3A-3A′ in FIG. 2, and FIG. 3(b) is a cross-sectional view taken alongline 3B-3B′ in FIG. 2. FIG. 3(c) is a cross-sectional view showing atapering angle θ of a side surface of each of the layers. FIG. 4(a)through FIG. 4(d) are each a schematic cross-sectional view of the OLEDdisplay device 100. FIG. 4(a) is a cross-sectional view taken along line4A-4A′ in FIG. 2. FIG. 4(b) is a cross-sectional view taken along line4B-4B′ in FIG. 2. FIG. 4(c) is a cross-sectional view taken along line4C-4C′ in FIG. 2. FIG. 4(d) is a cross-sectional view taken along line4D-4D′ in FIG. 2.

First, FIG. 2 will be referred to. The circuit 2 formed on the substrate1 includes a plurality of the TFTs (not shown), and a plurality of gatebus lines (not shown) and a plurality of source bus lines (not shown)each connected to either one of the plurality of TFTs (not shown). Thecircuit 2 may be a known circuit that drives the plurality of OLEDs 3.The plurality of OLEDs 3 are each connected with either one of theplurality of TFTs included in the circuit 2. The OLEDs 3 may be knownOLEDs.

The circuit 2 further includes a plurality of terminals 34 located in aperipheral region R2 outer to the active region (region enclosed by thedashed line in FIG. 2) where the plurality of OLEDs 3 are located, and aplurality of lead wires 32 connecting each of the plurality of terminals34 and either one of the plurality of gate bus lines or either one ofthe plurality of source bus lines to each other. The entirety of thecircuit 2 including the plurality of TFTs, the plurality of gate buslines, the plurality of source bus lines, the plurality of lead wires 32and the plurality of terminals 34 may be referred to as a “drivingcircuit layer 2”. A part of the driving circuit layer 2 that is formedin the active region R1 is represented as a “driving circuit layer 2A”.

In FIG. 2 and the like, only the lead wires 32 and/or only the terminals32 may be shown as components of the driving circuit layer 2.Nonetheless, the driving circuit layer 2 includes a conductive layerincluding the lead wires 32 and the terminals 34, and also includes atleast one conductive layer, at least one insulating layer and at leastone semiconductor layer. The structure of each of the conductive layer,the insulating layer and the semiconductor layer included in the drivingcircuit layer 2 may be changed by, for example, the structure of the TFTdescribed below with reference to FIG. 9(a) and FIG. 9(b). On thesubstrate 1, an insulating layer (base coat) may be formed as anunderlying film for the driving circuit layer 2.

As seen in a direction normal to the substrate 1, the organic flatteninglayer 2Pb is formed in a region where the inorganic protective layer 2Pais formed, and the active region R1 (2A, 3) is located in a region wherethe organic flattening layer 2Pb is formed. An outer perimeter of thethin film encapsulation structure 10 crosses the plurality of leadwires, and is present between an outer perimeter of the organicflattening layer 2Pb and an outer perimeter of the inorganic protectivelayer 2Pa. Therefore, the organic flattening layer 2Pb, together withthe OLED 3, is enclosed by a joint portion where the inorganicprotective layer 2Pa and the first inorganic barrier layer 12 are indirect contact with each other (see FIG. 3(b) and FIG. 4(b)). Theinorganic protective layer 2Pa is formed to expose at least theplurality of terminals 34. The inorganic protective layer 2Pa may beformed as follows: an inorganic protective film is once formed to coverthe terminals 34 and is subjected to a photolithography process to formthe inorganic protective layer 2Pa having an opening exposing theterminals 34.

The inorganic protective layer 2Pa protects the driving circuit layer 2.The organic flattening layer 2Pb flattens a surface of an underlyinglayer on which the OLED layer 3 is to be formed. Like the organicbarrier layer 14, the organic flattening layer 2Pb is lower in the watervapor barrier property than the inorganic protective layer 2Pa or theinorganic barrier layers 12 and 16. Therefore, in the case where anorganic flattening layer is partially exposed to the air (ambientatmosphere) like an organic flattening layer 2Pbc of an OLED displaydevice 100C shown in FIG. 6 through FIG. 8, moisture is absorbed by theorganic flattening layer from the part exposed to the air. As a result,the organic flattening layer 2Pbc acts as a route that guides watervapor in the air to the active region R1. As described above, in theOLED display device 100 in the embodiment, the organic flattening layer2Pb is enclosed by the joint portion where the inorganic protectivelayer 2Pa and the first inorganic barrier layer 12 are in direct contactwith each other. Therefore, moisture is prevented from being guided tothe active region R1 via the organic flattening layer 2Pb.

It is preferred that the organic flattening layer 2Pb is formed of aphotosensitive resin. The organic flattening layer 2Pb is formed by useof any of various coating methods and printing methods. The organicflattening layer 2Pb, in the case of being formed of a photosensitiveresin, is easily formed in a predetermined region by a photolithographyprocess. The photosensitive resin may be positive or negative. Aphotosensitive acrylic resin or a photosensitive polyimide resin ispreferably usable. In the case where a photoresist is used separately, aresin that is not photosensitive may be used to form the organicflattening layer 2Pb.

It is preferred to heat (bake) the organic flattening layer 2Pb in orderto remove moisture contained therein before the OLED layer 3 is formedon the organic flattening layer 2Pb. The heating temperature ispreferably, for example, higher than, or equal to, 200° C. (e.g., forlonger than, or equal to, 1 hour), and more preferably higher than, orequal to, 300° C. (e.g., for longer than, or equal to, 15 minutes). Theheating is preferably performed in a low pressure atmosphere, but may beperformed at an atmospheric pressure. It is preferred that the heatingis performed in an atmosphere of dry air or dry nitrogen having a dewpoint lower than, or equal to, −50° C. It is preferred that the resinmaterial used to form the organic flattening layer 2Pb is highlyheat-resistant so as not to be thermally deteriorated in the heating(baking) step. For example, the resin material is preferably polyimide.

After the organic flattening layer 2Pb is formed but before the OLEDlayer 3 is formed, an element substrate may be temporarily stored ortransported during the production. Namely, after the element substrateincluding the driving circuit layer 2, the inorganic protective layer2Pa and the organic flattening layer 2Pb is formed but before the OLEDlayer 3 is formed, there may be some time (for example, the elementsubstrate may be stored for at least one day, e.g., for several days) orthe element substrate may be transported to another plant. In order toprevent a surface of the organic flattening layer 2Pb from beingcontaminated during this period or to prevent dust from being attachedto the surface of the organic flattening layer 2Pb during thetransportation, an organic polymer film, for example, may be formed tocover the organic flattening layer 2Pb. It is preferred that the organicpolymer film is formed to cover the entirety of the organic flatteninglayer 2Pb.

A step of forming the organic polymer film includes, for example, a stepof supplying a solution of the organic polymer onto the organicflattening layer 2Pb. The solution of the organic polymer is supplied bya known coating method (e.g., spin coating or slot coating). A dry filmmay be used, but it is advantageous from the point of view of costs touse the solution of the organic polymer.

It is preferred that the organic polymer film is formed of awater-soluble polymer. The organic polymer film, in the case of beingformed of a water-soluble polymer, may be dissolved in an aqueoussolvent and thus is easily removed. The aqueous solvent suppressescontamination of the element substrate and also is environment-friendly,and allows the processing cost to be low.

Usable examples of the water-soluble polymer include known water-solublepolymers, for example, poly(vinyl alcohol) (PVA), polyacrylic acid-basedpolymer, poly(ethylene glycol) (PEG), poly(ethylene oxide) (PEO),poly(vinyl pyrrolidone) (PVP), poly(acrylamide) (PAM), gelatin,cellulose, and derivatives thereof. Among these, poly(vinyl alcohol) ispreferably usable.

Herein, the “aqueous solvent” refers to water, an organic solventmiscible with water, or a mixed solvent of water and an organic solventmiscible with water. Examples of the organic solvent miscible with waterinclude alcohol and ketone. Since it is preferred that the solvent has alow boiling point, the organic solvent miscible with water is preferablyalcohol having a small carbon number, for example, methanol or ethanol.

In the case where the organic polymer film is formed of poly(vinylalcohol), for example, a solution containing 3% by mass of poly(vinylalcohol) with respect to a solvent of pure water and methanol mixed at amass ratio of 6:4 is usable.

After this, the solution is left at a temperature lower than, or equalto, 100° C., for example, at 80° C., for about 30 minutes to volatilizeand thus remove the mixed solvent. It is preferred to volatilize andthus remove the mixed solvent to such a degree that a surface of theorganic polymer film does not become viscous. Alternatively, thesolution may be left at room temperature to volatilize and thus removethe mixed solvent.

The organic polymer film may be formed of any of various organicpolymers soluble in an organic solvent, needless to say. For example, aphotoresist is usable. It should be noted that the photoresist film doesnot need to be exposed to light. Therefore, the photoresist may bepositive or negative. For example, a photoresist solution (e.g., productname OFPR-800 produced by Tokyo Ohka Kogyo Co., Ltd.) may be suppliedand then prebaked (the solvent is volatilized and thus removed by, forexample, being heated in a temperature range of about 90° C. or higherto about 110° C. or lower for about 5 minutes to about 30 minutes) toform the organic polymer film.

It is preferred that the organic polymer film has a thickness of, forexample, 1 μm or greater and 5 μm or less. In the case where thethickness of the organic polymer film is less than 1 μm, the surface ofthe substrate may not be sufficiently protected. By contrast, in thecase where the thickness of the organic polymer film exceeds 5 μm, aninner stress of the organic polymer film may adversely affect theunderlying layer. In addition, there may be inconvenience that theorganic polymer film is cracked to spoil the protective functionthereof.

It is preferred that the method for producing the OLED display device100 described herein includes the above-described method of temporarilyprotecting the organic flattening layer by use of the organic polymerfilm. The method for producing the OLED display device 100 is notlimited thereto. Namely, it is sufficient that the method for producingthe OLED display device 100 includes a step of forming a driving circuitlayer on a substrate, a step of forming an inorganic protective layer onthe driving circuit layer, a step of forming an organic flattening layeron the inorganic protective layer, a step of heating the organicflattening layer to a temperature higher than, or equal to, 200° C., anda step of forming an organic EL element layer on the organic flatteninglayer after the step of heating, and further includes, after the organicflattening layer is formed but before the organic flattening layer isheated, a step of forming an organic polymer film covering the organicflattening layer and a step of removing the organic polymer film.

Now, with reference to FIG. 3(a) through FIG. 3(c) and FIG. 4(a) throughFIG. 4(d), the cross-sectional structure of the OLED display device 100will be described in more detail.

As shown in FIG. 3(a), FIG. 3(b), FIG. 4(a) and FIG. 4(b), the TFEstructure 10 includes the first inorganic barrier layer 12 formed on theOLED 3, the organic barrier layer 14 in contact with the first inorganicbarrier layer 12, and the second inorganic barrier layer 16 in contactwith the organic barrier layer 14. The first inorganic barrier layer 12and the second inorganic barrier layer 16 are each, for example, anSiN_(x) layer and are selectively formed in a predetermined region so asto cover the active region R1 by plasma CVD using a mask.

The organic barrier layer 14 may be formed by, for example, the methoddescribed in Patent Document 2 or 3. For example, a vapor-like ormist-like organic material (e.g., acrylic monomer) is supplied, in achamber, onto the element substrate maintained at a temperature lowerthan, or equal to, room temperature, is condensed on the elementsubstrate, and is located locally, namely, at a border between a sidesurface of a protruding portion and a flat portion of the firstinorganic barrier layer 12 by a capillary action or a surface tension ofthe organic material in a liquid state. Then, the organic material isirradiated with, for example, ultraviolet rays to form a solid portionof the organic barrier layer (e.g., acrylic resin layer) 14 in a borderregion in the vicinity of the protruding portion. The organic barrierlayer 14 formed by this method does not substantially include a solidportion in the flat portion. Regarding the method for forming theorganic barrier layer, the disclosures of Patent Documents 2 and 3 areincorporated herein by reference.

Alternatively, the organic barrier layer 14 may be formed by adjustingan initial thickness of the resin layer to be formed by use of the filmformation device 200 (e.g., to less than 100 nm) and/or by performing anashing process on the resin layer once formed. As described below, theashing process may be performed by plasma ashing using, for example, atleast one type of gas among N₂O, 0 ₂ and 0 ₃.

FIG. 3(a) is a cross-sectional view taken long line 3A-3A′ in FIG. 2,and shows a portion including a particle P. The particle P is amicroscopic dust particle generated during the production of the OLEDdisplay device, and is, for example, a microscopic piece of brokenglass, a metal particle or an organic particle. Such a particle iseasily generated in the case where mask vapor deposition is used.

As shown in FIG. 3(a), the organic barrier layer (solid portion) 14 maybe formed only in the vicinity of the particle P. A reason for this isthat the acrylic monomer supplied after the first inorganic barrierlayer 12 is formed is condensed and present locally, namely, in thevicinity of a surface of the first inorganic barrier layer 12 that is onthe particle P (the surface has a tapering angle larger than, or equalto, 90 degrees). There is the opening (non-solid portion) of the organicbarrier layer 14 on the flat portion of the first inorganic barrierlayer 12.

In the case where the particle P (having a diameter of, for example,greater than, or equal to, 1 μm) is present, the first inorganic barrierlayer 12 may have a crack (void) 12 c. This is considered to be causedby impingement of an SiN_(x) layer 12 a growing from a surface of theparticle P and an SiN_(x) layer 12 b growing from a flat portion of asurface of the OLED 3 In the case where such a crack 12 c is present,the barrier property level of the TFE structure 10 is decreased.

c Therefore, no void is caused in the first inorganic barrier layer 12on the particle P or in the second inorganic barrier layer 16 formed onthe organic barrier layer 14, and thus the first inorganic barrier layer12 and the second inorganic barrier layer 16 are formed to be fine. Ascan be seen, even in the case where the particle P is present, theorganic barrier layer 14 retains the barrier property level of the TFEstructure 10.

Now, with reference to FIG. 3(b) and FIG. 4(a) through FIG. 4(d), thecross-sectional structure on the lead wire 32 and the terminal 34 willbe described.

As shown in FIG. 3(b), the lead wire 32 and the terminal 34 areintegrally formed on the substrate 1. The inorganic protective layer 2Pais formed on the lead wire 32 so as to expose the terminal 34. On theinorganic protective layer 2Pa, the organic flattening layer 2Pb isformed. On the organic flattening layer 2Pb, the OLED layer 3 is formed.The TFE structure 10 is formed so as to cover the OLED layer 3 and theorganic flattening layer 2Pb. The OLED layer 3 and the organicflattening layer 2Pb are enclosed by the joint portion where theinorganic protective layer 2Pa and the first inorganic barrier layer 12are in direct contact with each other. The organic barrier layer (solidportion) 14 between the first inorganic barrier layer 12 and the secondinorganic barrier layer 16 of the TFE structure 10 is formed only aroundthe protruding portion such as the particle or the like, and thus is notshown in FIG. 3(b). The organic barrier layer (solid portion) 14 isenclosed by the inorganic barrier layer joint portion where the firstinorganic barrier layer 12 and the second inorganic barrier layer 16 arein direct contact with each other.

As shown in FIG. 4(a), in a region close to the active region R1(cross-section taken along line 4A-4A′ in FIG. 2), the inorganicprotective layer 2Pa, the organic flattening layer 2Pb and the TFEstructure 10 are formed on the lead wire 32.

As shown in FIG. 4(b), in a cross-section taken along line 4B-4B′ inFIG. 2, the inorganic protective layer 2Pa and the first inorganicbarrier layer 12 are in direct contact with each other, and the organicflattening layer 2Pb is enclosed by the joint portion where the jointportion where the inorganic protective layer 2Pa and the first inorganicbarrier layer 12 are in direct contact with each other (see FIG. 2 andFIG. 3(b)).

As shown in FIG. 4(c), in a region close to the terminal 34, only theinorganic protective layer 2Pa is formed on the lead wire 34.

As shown in FIG. 4(d), the terminal 34 is exposed from the inorganicprotective layer 2Pa and is used to electric connection with an externalcircuit (e.g., FPC (Flexible Printed Circuit)).

A region including the regions shown in FIG. 4(b) through FIG. 4(d) isnot covered with the organic flattening layer 2Pb. Therefore, in thisregion, the organic barrier layer (solid portion) may be formed duringthe formation of the organic barrier layer 14 of the TFE structure 10.For example, in the case where a side surface of a cross-section of thisregion taken along a plane parallel to a width direction of the leadwire 32 has a tapering angle θ larger than, or equal to, 90 degrees, theorganic barrier layer may be formed along a side surface of the leadwire 32. However, as shown in FIG. 4(b) through FIG. 4(d), in the OLEDdisplay device 100 in the embodiment, the tapering angle θ of the sidesurface of a cross-section of the lead wire 32 and the terminal 34 atleast in this region is smaller than 90 degrees, and no photocurableresin is present locally. Therefore, the organic barrier layer (solidportion) is not formed along the side surface of the lead wire 32 andthe terminal 34.

Now, with reference to FIG. 3(c), the tapering angle θ of the sidesurface of each of the layers will be described. FIG. 3(c) is across-sectional view showing the tapering angle θ of the side surface ofeach of the layers, and corresponds to, for example, the cross-sectionalview shown in FIG. 4(b). As shown in FIG. 3(c), the tapering angle ofthe side surface of the cross-section of the lead wire 32 taken alongthe width direction thereof is represented as θ(32). Regarding each ofthe other layers, the tapering angle of the side surface of thecross-section thereof taken along the width direction thereof isrepresented as θ (reference sign of the layer).

The tapering angles θ of the inorganic protective layer 2Pa formed onthe lead wire 32, and the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 of the TFE structure 10 formed on theinorganic protective layer 2Pa satisfy the relationship of θ(32) θ(2Pa)θ(12) θ(16). Therefore, in the case where the tapering angle θ(32) ofthe side surface of the lead wire 32 is smaller than 90 degrees, thetapering angle of the side surface of the inorganic protective layer2Pa, namely, θ(2Pa), and the tapering angle of the side surface of thefirst inorganic barrier layer 12, namely, θ(12), are also smaller than90 degrees.

In the case where the tapering angles of the side surfaces are largerthan, or equal to, 90 degrees, if the method for forming the organicbarrier layer described in Patent Document 2 or 3 is used, a vapor-likeor mist-like organic material (e.g., acrylic monomer) is condensed alonga border between the side surface and the flat surface (making an anglesmaller than, or equal to, 90 degrees), and thus the organic barrierlayer (solid portion) is formed. When this occurs, for example, theorganic barrier layer (solid portion) formed along the lead wire acts asa route that guides water vapor in the air to the active region.

As shown in FIG. 5(a), which is a schematic cross-sectional view of anOLED display device 100B1 in a comparative example and corresponds toFIG. 4(b), in the case where a tapering angle θ(32B1) of a side surfaceof a lead wire 32B1 and a tapering angle θ(12B1) of a side surface of afirst inorganic barrier layer 12B1 are each larger than, or equal to, 90degrees, an organic barrier layer (solid portion) 14B1 is formed along aside surface of the first inorganic barrier layer 12B1 of a TFEstructure 10B1, between the first inorganic barrier layer 12B1 and asecond inorganic barrier layer 16B1. The OLED display device 10B1, forexample, may be altered from the OLED display device 100 in theabove-described embodiment such that the inorganic protective layer Pa2is omitted and such that the tapering angle θ(32) of the side surface ofthe lead wire 32 and the tapering angle θ(12) of the side surface of thefirst inorganic barrier layer 12 are each changed to be larger than, orequal to, 90 degrees.

As shown in FIG. 5(b), which is a schematic cross-sectional view of anOLED display device 100B2 in a comparative example and corresponds toFIG. 4(b), in the case where tapering angles θ(32B2), θ(2PaB2) andθ(12B2) of side surfaces of a lead wire 32B2, an inorganic protectivelayer 2PaB2 and a first inorganic barrier layer 12B2 are each largerthan, or equal to, 90 degrees, an organic barrier layer (solid portion)14B2 is formed along a side surface of the first inorganic barrier layer12B2 of a TFE structure 10B2, between the first inorganic barrier layer12B2 and a second inorganic barrier layer 16B2. The OLED display device10B2, for example, may be altered from the OLED display device 100 inthe above-described embodiment such that the tapering angle θ(32) of theside surface of the lead wire 32 and the tapering angle θ(12) of theside surface of the first inorganic barrier layer 12 are each changed tobe larger than, or equal to, 90 degrees.

Unlike the OLED display device 100B1, the OLED display device 100B2includes the inorganic protective layer 2PaB2. Therefore, the taperingangle θ(12B2) of the side surface of the first inorganic barrier layer12B2 tends to be smaller than the tapering angle θ(12B1) of the firstinorganic barrier layer 12B1 of the OLED display device 100B1.

In the OLED display device 100 according to the above-describedembodiment of the present invention shown in FIG. 4(b) through FIG.4(d), the tapering angles θ(32), θ(2Pa) and θ(12) of the side surfacesof the lead wire 32, the inorganic protective layer 2Pa and the firstinorganic barrier layer 12 are all smaller than 90 degrees. Thus, theorganic barrier layer 14 is not formed along these side surfaces.Therefore, moisture in the air does not reach the inside of the activeregion R1 via the organic barrier layer (solid portion) 14, and thus thedisplay device 100 may have a high level of moisture-resistantreliability. In this example, the tapering angles θ(32), θ(2Pa) andθ(12) are all smaller than 90 degrees. The present invention is notlimited to this. As long as the tapering angle θ(12) of the side surfaceof the first inorganic barrier layer 12 that forms a surface immediatelybelow the inorganic barrier layer 14 is smaller than 90 degrees, thestack structure shown in FIG. 4(b) is formed; namely, the followingportions are formed: a portion where the inorganic protective layer 2Paand the first inorganic barrier layer 12 are in direct contact with eachother (the organic flattening layer 2Pb is absent), and a portion wherethe first inorganic barrier layer 12 and the second inorganic barrierlayer 16 are in direct contact with each other (the organic barrierlayer 14 is absent). Therefore, moisture in the air is suppressed orprevented from entering the inside of the active region R1 via theorganic flattening layer 2Pb or the organic barrier layer 14. Theprovision of the inorganic protective layer 2Pa decreases the taperingangle θ(12) of the first inorganic barrier layer 12. Therefore, even ifthe tapering angle θ(32) of the lead wire 32 is relatively large (e.g.,90 degrees), the tapering angle θ(12) of the first inorganic barrierlayer 12 is allowed to be smaller than 90 degrees. Namely, the taperingangle θ(32) of the lead wire 32 is allowed to be 90 degrees or close to90 degrees. This provides an advantage that the L/S of the lead wire 32is decreased.

In the case where the tapering angle θ of the side surface is in therange of 70 degrees or larger and smaller than 90 degrees, the organicbarrier layer (solid portion) 14 may be formed along the side surface.Needless to say, the resin present locally, namely, along the incliningside surface, is removed by ashing. However, the ashing istime-consuming. For example, the ashing needs to be performed for a longtime even after the resin formed on the flat surface is removed. Inaddition, there may be a problem that as a result of the organic barrierlayer (solid portion) formed in the vicinity of the particle P beingexcessively asked (removed), the effect of the formation of the organicbarrier layer is not sufficiently provided. In order to suppress orprevent this problem, the tapering angle θ(12) of the first inorganicbarrier layer 12 is preferably smaller than 70 degrees, and morepreferably smaller than 60 degrees.

Now, with reference to FIG. 6 through FIG. 8, a structure of the OLEDdisplay device 100C in a comparative example will be described. FIG. 6is a schematic plan view of the OLED display device 100C. FIG. 7(a) andFIG. 7(b) are each a schematic cross-sectional view of the OLED displaydevice 100C. FIG. 7(a) is a cross-sectional view taken along line 7A-7A′in FIG. 6, and FIG. 7(b) is a cross-sectional view taken along line7B-7B′ in FIG. 6. FIG. 8(a) through FIG. 8(c) are each a schematiccross-sectional view of the OLED display device 100C. FIG. 8(a) is across-sectional view taken along line 8A-8A′ in FIG. 6, FIG. 8(b) is across-sectional view taken along line 8B-8B′ in FIG. 6, and FIG. 8(c) isa cross-sectional view taken along line 8C-8C′ in FIG. 6.

Unlike the OLED display device 100 in the above-described embodiment,the OLED display device 100C does not include the inorganic protectivelayer 2Pa, and includes an organic flattening layer 2Pbc extending to aregion not covered with the TFE structure 10. Components that aresubstantially the same as those in the OLED display device 100 will bearidentical reference signs thereto and descriptions thereof will beomitted.

As is clear from, for example, FIG. 6, FIG. 7(b) and FIG. 8(b), a partof the organic flattening layer 2Pbc is exposed to the air (ambientatmosphere). In this case, the organic flattening layer 2Pbc absorbsmoisture from the part exposed to the air and acts as a route thatguides water vapor in the air onto the active region R1. By contrast, inthe OLED display device 100 in the above-described embodiment, as shownin FIG. 3(b) and FIG. 4(b), the organic flattening layer 2Pb, togetherwith the OLED layer 3, is enclosed by the joint portion where theinorganic protective layer 2Pa and the first inorganic barrier layer 12are in direct contact with each other. Therefore, the above-describedproblem of the OLED display device 100C in the comparative example issolved in the OLED display device 100.

Now, with reference to FIG. 9 and FIG. 10, an example of TFT usable inthe OLED display device 100, and an example of lead wire and terminalformed by use of a gate metal layer and a source metal layer used toform the formation of the TFT, will be described. The structures of theTFT, the lead wire and the terminal described below are usable for theOLED display device 100 in the above-described embodiment.

For a small- or medium-sized high-definition OLED display device, a lowtemperature polycrystalline silicon (hereinafter, referred to simply as“LTPS”) TFT or an oxide TFT (e.g., four-component-based(In—Ga—Zn—O-based) oxide TFT containing In (indium), Ga (gallium), Zn(zinc) and O (oxygen)) is preferably used. Structures of, and methodsfor producing, the LTPS-TFT and the In—Ga—Zn—O-based TFT are well knownand will be briefly described below.

FIG. 9(a) is a schematic cross-sectional view of an LTPS-TFT 2 _(P)T.The TFT 2 _(P)T may be included in the circuit 2 of the OLED displaydevice 100. The LTPS-TFT 2 _(P)T is a top gate-type TFT.

The TFT 2 _(P)T is formed on a base coat 2 _(P)p on the substrate 1(e.g., polyimide film). Although not described above, it is preferredthat a base coat formed of an inorganic insulating material is formed onthe substrate 1.

The TFT 2 _(P)T includes a polycrystalline silicon layer 2 _(P)se formedon the base coat 2 _(P)p, a gate insulating layer 2 _(P)gi formed on thepolycrystalline silicon layer 2 _(P)se, a gate electrode 2 _(P)g formedon the gate insulating layer 2 _(P)gi, an interlayer insulating layer 2_(P)i formed on the gate electrode 2 _(P)g, and a source electrode 2_(P)ss and a drain electrode 2 _(P)sd formed on the interlayerinsulating layer 2 _(P)i. The source electrode 2 _(P)ss and the drainelectrode 2 _(P)sd are respectively connected with a source region and adrain region of the polycrystalline silicon layer 2 _(P)se in contactholes formed in the interlayer insulating layer 2 _(P)i and the gateinsulating layer 2 _(P)gi.

The gate electrode 2 _(P)g is contained in the gate metal layercontaining the gate bus lines, and the source electrode 2 _(P)ss and thedrain electrode 2 _(P)sd are contained in the source metal layercontaining the source bus lines. The gate metal layer and the sourcemetal layer are used to form the lead wire and the terminal (describedbelow with reference to FIG. 10).

The TFT 2 _(P)T is formed, for example, as follows.

As the substrate 1, a polyimide film having a thickness of 15 μm, forexample, is prepared.

The base coat 2 _(P)p (SiO₂ film: 250 nm/SiN_(x) film: 50 nm/SiO₂ film:500 nm (top layer/middle layer/bottom layer)) and an a-Si film (40 nm)are formed by plasma CVD.

The a-Si film is subjected to dehydrogenation (e.g., annealed at 450° C.for 180 minutes).

The a-Si film is made polycrystalline-siliconized by excimer laserannealing (ELA).

The a-Si film is patterned by a photolithography step to form an activelayer (semiconductor island).

A gate insulating film (SiO₂ film: 50 nm) is formed by plasma CVD.

A channel region of the active layer is doped with (B⁺).

The gate metal layer (Mo: 250 nm) is formed by sputtering and patternedby a photolithography step (including a dry etching step) (to form thegate electrode 2 _(P)g, the gate bus lines, and the like).

A source region and a drain region of the active layer are doped with(P⁺).

Activation annealing (e.g., annealing at 450° C. for 45 minutes) isperformed. As a result, the polycrystalline silicon layer 2 _(P)se isformed.

An interlayer insulating film (e.g., SiO₂ film: 300 nm/SiN_(x) film: 300nm (top layer/bottom layer)) is formed by plasma CVD.

The contact holes are formed in the gate insulating film and theinterlayer insulating film by dry etching. As a result, the interlayerinsulating layer 2 _(P)i and the gate insulating layer 2 _(P)gi areformed.

The source metal layer (Ti film: 100 nm/Al film: 300 nm/Ti film: 300 nm)is formed by sputtering and patterned by a photolithography step(including a dry etching step) (to form the source electrode 2 _(P)ss,the drain electrode 2 _(P)sd, the source bus lines, and the like).

After this, the above-described inorganic protective layer 2Pa (see FIG.2 and FIG. 3) is formed.

FIG. 9(b) is a schematic cross-sectional view of an In—Ga—Zn—O-based TFT2 _(O)T. The TFT 2 _(O)T may be included in the circuit 2 of an OLEDdisplay device 100A. The 2 _(O)T is a bottom gate-type TFT.

The TFT 2 _(O)T is formed on a base coat 2 _(O)p on the substrate 1(e.g., polyimide film). The TFT 2 _(O)T includes a gate electrode 2_(O)g formed on the base coat 2 _(O)p, a gate insulating layer 2 _(O)giformed on the gate electrode 2 _(O)g, an oxide semiconductor layer 2_(O)se formed on the gate insulating layer 2 _(O)gi, and a sourceelectrode 2 _(O)ss and a drain electrode 2 _(O) sd respectively formedon a source region and a drain region of the oxide semiconductor layer 2_(O)se. The source electrode 2 _(O)ss and the drain electrode 2 _(O) sdare covered with an interlayer insulating layer 2 _(O) i.

The gate electrode 2 _(O)g is contained in the gate metal layercontaining the gate bus lines, and the source electrode 2 _(O)ss and thedrain electrode 2 _(O) sd are contained in the source metal layercontaining the source bus lines. The gate metal layer and the sourcemetal layer are used to form the lead wire and the terminal, and thusthe TFT 2 _(O)T may have the structure described below with reference toFIG. 10.

The TFT 2 _(O)T is formed, for example, as follows.

As the substrate 1, a polyimide film having a thickness of 15 μm, forexample, is prepared.

The base coat 2 _(O)p (SiO₂ film: 250 nm/SiN_(x) film: 50 nm/SiO₂ film:500 nm (top layer/middle layer/bottom layer)) is formed by plasma CVD.

The gate metal layer (Cu film: 300 nm/Ti film: 30 nm (top layer/bottomlayer)) is formed by sputtering and patterned by a photolithography step(including a dry etching step) (to form the gate electrode 2 _(O)g, thegate bus lines, and the like).

A gate insulating film (SiO₂ film: 30 nm/SiN_(x) film: 350 nm (toplayer/bottom layer)) is formed by plasma CVD.

An oxide semiconductor film (In—Ga—Z—O-based semiconductor film: 100 nm)is formed by sputtering and patterned by a photolithography step(including a wet etching step) to form an active layer (semiconductorisland).

The source metal layer (Ti film: 100 nm/Al film: 300 nm/Ti film: 30 nm(top layer/medium layer/bottom layer)) is formed by sputtering andpatterned by a photolithography step (including a dry etching step) (toform the source electrode 2 _(O)ss, the drain electrode 2 _(O)sd, thesource bus lines, and the like).

Activation annealing (e.g., annealing at 300° C. for 120 minutes) isperformed. As a result, the oxide semiconductor layer 2 _(O)se isformed.

After this, the interlayer insulating layer 2 _(O)i (e.g., SiN_(x) film:300 nm/SiO₂ film: 300 nm (top layer/bottom layer)) is formed by plasmaCVD as a protection film. The interlayer insulating layer 2 _(O)i mayalso act as the inorganic protective layer 2Pa (see FIG. 2 and FIG. 3)described above. Needless to say, the inorganic protective layer 2Pa mayfurther be formed on the interlayer insulating layer 2 _(O) i.

Now, with reference to FIG. 10(a) through FIG. 10(c), a structure ofanother OLED display device in an embodiment will be described. Thecircuit (back plane circuit) 2 of this OLED display device includes theTFT 2 _(P)T shown in FIG. 9(a) or the TFT 2 _(O)T shown in FIG. 9(b).The gate metal layer and the source metal layer used to form the TFT 2_(P)T or the TFT 2 _(O)T is used to form a lead wire 32A and a terminal34A. FIG. 10(a) through FIG. 10(c) respectively correspond to FIG. 4(b)through FIG. 4(d). Components corresponding to those in FIG. 4(b)through FIG. 4(d) will be represented by the identical reference signsprovided with a letter “A” at the end. A base coat 2 p in FIG. 10corresponds to the base coat 2 _(P)p in FIG. 9(a) and the base coat 2 opin FIG. 9(b). A gate insulating layer 2 gi in FIG. 10 corresponds to thegate insulating layer 2 _(P)gi in FIG. 9(a) and the gate insulatinglayer 2 _(O)gi in FIG. 9(b). An interlayer insulating layer 2 i in FIG.10 corresponds to the interlayer insulating layer 2 _(P)i in FIG. 9(a)and the interlayer insulating layer 2 _(O) i in FIG. 9(b).

As shown in FIG. 10(a) through FIG. 10(c), a gate metal layer 2 g and asource metal layer 2 s are formed on the base coat 2 p, which is formedon the substrate 1. Although not shown in FIG. 3 or FIG. 4, it ispreferred a base coat formed of an inorganic insulating material isformed on the substrate 1.

As shown in FIG. 10(a) through FIG. 10(c), the lead wire 32A and theterminal 34A are formed as a stack body of the gate metal layer 2 g andthe source metal layer 2 s. A part of each of the lead wire 32A and theterminal 34A that is formed of the gate metal layer 2 g has, forexample, the same cross-sectional structure as that of the gate buslines. A part of each of the lead wire 32A and the terminal 34A that isformed of the source metal layer 2 s has, for example, the samecross-sectional structure as that of the source bus lines. In a case ofa 5.7-type display device of 500 ppi, the part formed of the gate metallayer 2 g has a line width of, for example, 10 μm, and a distancebetween two adjacent such lines is 16 μm (L/S=10/16). The part formed ofthe source metal layer 2 s has a line width of, for example, 16 μm, anda distance between two adjacent such lines is 10 μm (L/S=16/10). Thetapering angle θ of each of the parts is smaller than 90 degrees,preferably smaller than 70 degrees, and more preferably smaller than, orequal to, 60 degrees. The tapering angle of a part formed below theorganic flattening layer Pb may be larger than, or equal to, 90 degrees.

Now, with reference to FIG. 11(a) and FIG. 11(b), a film formationdevice 200 usable to form an organic barrier layer, and a film formationmethod using the same will be described. FIG. 11(a) and FIG. 11(b)schematically show a structure of the film formation device 200. FIG.11(a) shows a state of the film formation device 200 in a step of, in achamber having a vapor-like or mist-like photocurable resin locatedtherein, condensing the photocurable resin on the first inorganicbarrier layer. FIG. 11(b) shows a state of the film formation device 200in a step of irradiating the photocurable resin with light to which thephotocurable resin is sensitive and thus curing the photocurable resin.

The film formation device 200 includes a chamber 210 and a partitionwall 234 dividing the inside of the chamber 210 into two spaces. In oneof the spaces demarcated by the partition wall 234, a stage 212 and ashower plate 220 are located. In the other space demarcated by thepartition wall 234, an ultraviolet ray irradiation device 230 islocated. The inner space of the chamber 210 is controlled to have apredetermined pressure (vacuum degree) and a predetermined temperature.The stage 212 has a top surface that receives an element substrate 20including a plurality of OLEDs 3, on which the first inorganic barrierlayer is formed. The top surface may be cooled down to, for example,−20° C.

The shower plate 220 is located to have a gap 224 between the showerplate 220 and the partition wall 234. The shower plate 220 has aplurality of through-holes 222. The gap 224 may have a size of, forexample, 100 mm or greater and 1000 mm or less in a vertical direction.An acrylic monomer (in a vapor or mist state) supplied to the gap 224 issupplied, via the plurality of through-holes 222 of the shower plate220, to one of the spaces of the chamber 210 in which the stage 212 islocated. As necessary, the acrylic monomer is heated. The vapor-like ormist-like acrylic monomer 26 p is attached to, or contacts, the firstinorganic barrier layer included in the element substrate 20. Theacrylic monomer 26 p is supplied from a container 202 into the chamber210 at a predetermined flow rate. The container 202 is supplied with theacrylic monomer 26 p via a pipe 206 and also is supplied with nitrogengas from a pipe 204. The flow rate of the acrylic monomer supplied tothe container 202 is controlled by a mass flow controller 208. Amaterial supply device includes the shower plate 220, the container 202,the pipes 204 and 206, the mass flow controller 208 and the like.

The ultraviolet ray irradiation device 230 includes an ultraviolet raysource and an optional optical element. The ultraviolet ray source maybe, for example, an ultraviolet lamp (e.g., mercury lamp (encompassing ahigh-pressure lamp and a super-high pressure lamp), a mercury-xenon lampor a metal halide lamp). The optical element includes, for example, areflective mirror, a prism, a lens and a diffractive element.

The ultraviolet ray irradiation device 230, when being located at apredetermined position, directs light having a predetermined wavelengthand a predetermined intensity toward the top surface of the stage 212.It is preferred that the partition wall 234 and the shower plate 220 areformed of a material having a high ultraviolet transmittance, forexample, quartz.

The organic barrier layer 14 may be formed, for example, as follows byuse of the film formation device 200. In this example, an acrylicmonomer is used as the photocurable resin.

The acrylic monomer 26 p is supplied into the chamber 210. The elementsubstrate 20 has been cooled to, for example, −15° C. on the stage 212.The acrylic monomer 26 p is condensed on the first inorganic barrierlayer 12 in the element substrate 20. The conditions in this step may becontrolled such that the acrylic monomer in a liquid state is presentlocally, namely, only around the protruding portion of the firstinorganic barrier layer 12. Alternatively, the conditions may becontrolled such that the acrylic monomer condensed on the firstinorganic barrier layer 12 forms a liquid film.

The viscosity and/or the surface tension of the photocurable resin inthe liquid state may be adjusted to control the thickness of the liquidfilm or the shape of the portion of the liquid film that is to be incontact with the protruding portion of the first inorganic barrier layer12 (namely, the shape of the recessed portion). For example, theviscosity and the surface tension depend on the temperature. Therefore,the temperature of the element substrate may be adjusted to control theviscosity and the surface tension. For example, the size of the solidportion present on the flat portion may be controlled by the shape of apart of the liquid film that is to be in contact with the protrudingportion of the first inorganic barrier layer 12 (namely, the shape ofthe recessed portion) and by the conditions of ashing to be performed ina later step.

Next, the acrylic monomer on the first inorganic barrier layer 12 iscured by use of the ultraviolet ray irradiation device 230, typically,by directing ultraviolet rays 232 toward the entirety of a top surfaceof the element substrate 20. As the ultraviolet ray source, for example,a high pressure mercury lamp that provides light having a main peak at365 nm is used. The ultraviolet rays are directed at an intensity of,for example, 12 mW/cm² for about 10 seconds.

The organic barrier layer 14 of an acrylic resin is formed in thismanner. The tact time of the step of forming the organic barrier layer14 is shorter than about 30 seconds. Thus, the mass-productivity is veryhigh.

Alternatively, after the photocurable resin in the liquid state is curedand ashing is performed, the organic barrier layer 14 may be formed onlyaround the protruding portion. Even in the case where the organicbarrier layer 14 is formed by curing the photocurable resin presentlocally, ashing may be performed. The ashing may improve theadhesiveness between the organic barrier layer 14 and the secondinorganic barrier layer 16. Namely, the ashing may be used to modify(make hydrophilic) the surface of the organic barrier layer 14, as wellas to remove an excessive portion of the organic barrier layer formed.

The ashing may be performed by use of a known plasma ashing device, aknown photoexcitation ashing device, or a known UV ozone ashing device.For example, plasma ashing using at least one type of gas among N₂O, 0 ₂and 0 ₃, or a combination of such plasma ashing and ultraviolet rayirradiation, may be performed. In the case where an SiN_(x) film isformed by CVD as the first inorganic barrier layer 12 and the secondinorganic barrier layer 16, N20 is used as a material gas. Therefore,use of N20 for the ashing provides an advantage that the device issimplified.

In the case where the ashing is performed, the surface of the organicbarrier layer 14 is oxidized and thus is modified to be hydrophilic. Inaddition, the surface of the organic barrier layer 14 is shaved almostuniformly and extremely tiny ruggedness is formed, and thus the surfacearea size is enlarged. The effect of enlarging the surface area sizeprovided by the asking is greater for the surface of the organic barrierlayer 14 than for the first inorganic barrier layer 12 formed of aninorganic material. Since the surface of the organic barrier layer 14 ismodified to be hydrophilic and the surface area size thereof isenlarged, the adhesiveness of the organic barrier layer 14 with thesecond inorganic barrier layer 16 is improved.

After the above, the resultant body is transported to a CVD chamber inorder to form the second inorganic barrier layer 16. The secondinorganic barrier layer 16 is formed under, for example, the sameconditions for the first inorganic barrier layer 12. The secondinorganic barrier layer 16 is formed in the region where the firstinorganic barrier layer 12 is formed. Therefore, the inorganic barrierlayer joint portion were the first inorganic barrier layer 12 and thesecond inorganic barrier layer 16 are in direct contact with each otheris formed in the non-solid portion of the organic barrier layer 14.Therefore, as described above, water vapor in the air is suppressed orprevented from reaching the inside of the active region via the organicbarrier layer.

The first inorganic barrier layer 12 and the second inorganic barrierlayer 16 are formed, for example, as follows. An inorganic barrier layerhaving a thickness of 400 nm may be formed by plasma CVD using SiH₄ gasand N₂O gas, at a film formation rate of 400 nm/min, in a state where,for example, the temperature of the substrate as a target of the filmformation (OLED 3) is controlled to be lower than, or equal to, 80° C.The inorganic barrier layer thus formed has a refractive index of 1.84and a 400 nm visible light transmittance of 90% (thickness: 400 nm). Thefilm stress has an absolute value of 50 MPa.

The inorganic barrier layer may be an SiO₂ layer, an SiO_(x)N_(y) (x>y)layer, an SiN_(x)O_(y) (x>y) layer, an Al₂O₃ layer or the like as wellas an SiN_(x) layer. The photocurable resin contains, for example, avinyl group-containing monomer. Among such monomers, an acrylic monomeris preferably used. The acrylic monomer may be mixed with aphotoinitiator when necessary. Any of various known acrylic monomers isusable. A plurality of acrylic monomers may be mixed. For example, abifunctional monomer and a trifunctional or higher-levelmulti-functional monomer may be mixed. An oligomer may be mixed. Theviscosity of the photocurable resin at room temperature (e.g., 25° C.),before the photocurable resin is cured, preferably does not exceed 10Pa·s, and especially preferably is in 1 to 100 mPa·s. In the case wherethe viscosity is too high, it may be difficult to form a thin liquidfilm having a thickness less than, or equal to, 500 nm.

In the above, an OLED display device including a flexible substrate anda method for producing the same are described. An embodiment of thepresent invention is not limited to the devices or methods describedabove. An embodiment of the present invention is widely applicable to anorganic EL device including an organic EL element including anon-flexible substrate (e.g., glass substrate) and a thin filmencapsulation structure formed on the organic EL element (for example,to an organic EL illumination device).

INDUSTRIAL APPLICABILITY

An embodiment of the present invention is applicable to an organic ELdevice and a method for producing the same. Especially, an embodiment ofthe present invention is applicable to a flexible organic EL displaydevice and a method for producing the same.

REFERENCE SIGNS LIST

-   -   1: Flexible substrate    -   2: Back plane (circuit)    -   3: Organic EL element    -   4: Polarization plate    -   10: Thin film encapsulation structure (TFE structure)    -   12: First inorganic barrier layer (SiN_(x) layer)    -   14: Organic barrier layer (acrylic resin layer)    -   16: Second inorganic barrier layer (SiN_(x) layer)    -   20 Element substrate    -   26: Acrylic monomer    -   26 p: Vapor-like or mist-like acrylic monomer    -   100, 100C: Organic EL display device    -   200 Film formation device

1. A method for producing an organic electroluminescent device, theorganic electroluminescent device including a substrate; a drivingcircuit layer including a plurality of TFTs formed on the substrate, aplurality of gate bus lines and a plurality of source bus lines eachconnected with any of the plurality of TFTs, a plurality of terminals,and a plurality of lead wires connecting each of the plurality ofterminals with either one of the plurality of gate bus lines or eitherone of the plurality of source bus lines; an inorganic protective layerformed on the driving circuit layer and exposing at least the pluralityof terminals; an organic flattening layer formed on the inorganicprotective layer; an organic electroluminescent element layer formed onthe organic flattening layer and including a plurality of organicelectroluminescent elements each connected with either one of theplurality of TFTs; and a thin film encapsulation structure formed tocover the organic electroluminescent element layer; the methodcomprising: step A of forming the driving circuit layer on thesubstrate; step B of forming the inorganic protective layer on thedriving circuit layer; step C of forming the organic flattening layer onthe inorganic protective layer; step D of reducing moisture contained inthe organic flattening layer; step E of forming the organicelectroluminescent element layer on the organic flattening layer afterthe step D; and step C1 of forming an organic polymer film covering theorganic flattening layer and step C2 of removing the organic polymerfilm, the step C1 and the step C2 being performed after the step C butbefore the step D.
 2. The method of claim 1, wherein the step Dcomprises the step of heating the organic flattening layer in a lowpressure atmosphere or at an atmospheric pressure.
 3. The method ofclaim 1, wherein the step D is performed in an atmosphere of dry air ordry nitrogen having a dew point lower than or equal to −50° C.
 4. Themethod of claim 1, wherein the step C1 comprises the step of supplying asolution containing a water-soluble polymer and an aqueous solvent ontothe organic flattening layer, and the step of volatilizing the aqueoussolvent contained in the solution at a temperature lower than or equalto 100° C.
 5. The method of claim 4, wherein the aqueous solventcontains methanol or ethanol.
 6. The method of claim 4, wherein thewater-soluble polymer is poly(vinyl alcohol).
 7. The method of claim 1,wherein the organic flattening layer is formed of a photosensitiveresin.
 8. The method of claim 1, wherein the organic flattening layer isformed of polyimide.
 9. The method of claim 1, further comprising thestep of storing or transporting the substrate having the organic polymerfilm formed thereon between the step C1 and the step C2.